…with the sole exception of its Netzach-Hod-Yesod… For the same relationship always applies whereby the lowest part of the upper level is what becomes the interior soul of the lower level. Only Netzach-Hod-Yesod of the upper Partzuf can enter into the lower Partzuf because this alone can descend to the level of the lower Partzuf so as to serve as its inner soul. Thus only Netzach-Hod-Yesod of the overall entity enter into Zeir Anpin.
…while the rest stays outside… Zeir Anpin is unable to receive it within him because the light would be too close to the vessel and in excess of what the vessel is capable of concealing and holding within limits.